Leaf measurements from New Caledonian conifers

Premise: The archipelago of New Caledonia contains one of the world's
most distinctive biotas. The presence of notable paleoendemic taxa
suggests Gondwanan vicariance may have played an important role in the
formation of New Caledonia's biota, but geological evidence indicates
that the landmass was submerged until the Oligocene and its flora resulted
from more recent long-distance dispersal events. The lack of a fossil
record contributes to uncertainties inherent in both interpretations, but
newly discovered fossil plant assemblages may help to clarify the origins
of the New Caledonian flora. Methods: We use standard paleobotanical
techniques to prepare and describe leafy conifer shoots from an early
Miocene deposit (~19 Ma) on the Pindaï Peninsula of western New Caledonia.
To determine affinities of the fossil material, we compare it to herbarium
collections of extant New Caledonian conifers and the broader macrofossil
record. Results: Fossil leaves contain cellular-level details of leaf
morphology and epidermis anatomy, which are consistent with the conifer
family Podocarpaceae, particularly the extant genus Dacrycarpus. Stomata
in the fossils are arranged in crowded complexes unlike those of any
described Podocarpaceae taxon, however, and we assign this material to a
new extinct genus Dacrycarpoides. Conclusions: New Caledonia is a hotspot
of modern conifer biodiversity and was home to now-extinct lineages as
well. The presence of extinct conifers on Miocene New Caledonia is
consistent with floras from neighboring landmasses and highlights the role
of extinction in shaping the modern flora of New Caledonia and other
Australasian landmasses.